There are two parts to this:
- First, a way to retrieve any signature from a DXBC shader. This is, I gather, generally useful for reflection, and it can be used as one source with which to implement d3d10 and d3d11 shader reflection APIs.
The rest of those APIs will need much more data to be exposed from d3d shaders, and while I was originally planning to expose that all in a single "vkd3d_shader_d3d_shader_info" structure, I think that signatures at least are a reasonable enough subset to have a dedicated structure. Moreover, I did not want to block sm1 support on too much API design.
- Second, signatures synthesized from sm1 byte code. This is conceptually a bit weird, because sm1 does not have signatures, but in terms of how these APIs are used by Wine (or other translation layers, as evidenced not least by the Vulkan test shader runner, which I have locally adapted for sm1 but not submitted yet) it fits rather nicely.
Because this is new API, it of course deserves plenty of discussion, especially the sm1 part. Several open questions which occurred to me while writing are:
1. Should we fix the mask (and used mask) for sm1 signatures as 0xf rather than 0? SPIR-V cares about this in order to declare I/O variables, which makes some amount of sense. In fact I have a patch in my local tree to change this, specifically for that purpose. However, we could also normalize it later.
2. If we do fix the mask as nonzero, should single-component semantics (fog, depth, etc...) be declared as 0x1 instead of 0xf?
3. Should BLENDINDICES get a UINT type? It's float in shader instructions (well, kind of, although in practice it's used as an array index of course), but the vertex attribute type is in practice "supposed" to be integer.
Part 1 of a series to implement sm1 -> spirv translation in vkd3d-shader, brought to you by late nights spent coding and rereading The Waste Land.
Ganga was sunken, and the limp leaves Waited for rain, while the black clouds Gathered far distant, over Himavant.
-- v5: vkd3d-shader: Synthesize signatures for d3dbc shaders. vkd3d-shader: Introduce an API to retrieve all signatures from DXBC shaders. vkd3d-shader: Introduce documented semantics for the target type and other data passed to vkd3d_shader_scan().